This is a proposed variant to add into the symbol file lk.
It has been tested and works as expected. The text below is
in three parts. 

1. The variant program for inclusion at the bottom of the
   symbols lk file.
2. The portion to be added to base.xml at the following
   location:
   <layout> -> <name>lk</name> -> <variantList>
   add the lines just above the closing tag </variantList>
3. Add the given line under '! variant' section as the first
   alphabetically listed variant for lk

Thank you most humbly.

JC

PROPOSED ADDITIONS:
1. Please add the following program to the end of lk symbols file

=============PLEASE ADD AT BOTTOM OF symbols/lk FILE==============


// SINGHALA - US, SUBSTITUTES SOME AND ADDS SOME
// =============================================
//
// This started as an upgrade to the first romanized version of
// Singhala called PTS Pali created in the 1860s. PTS requires
// dots and bars on letters that are rare in fonts, and impossible
// to type. Its singular purpose was to print Tripitaka, the
// collection of Buddhist discourses.
//
// This version covers the entire newer Singhala phoneme chart
// (Hodiya) that became standard just before the end of the 19th
// century. All the phonemes map to the SBCS. It is easy and
// faster than English to type. It overcomes the setback of
// Unicode Sinhala that it is not compatible with Pali and
// Sanskrit because it encodes two ligatures as base letters and
// the SLS1134 specification matching shape and morpheme sets
// violating Sanskrit orthography.
//
// Most importantly, this romanized version of Singhala has a
// companion orthographic font that displays the text in the
// native script and a JavaScript converts it to Unicode Sinhala
// and back dramatically increasing Singhala seen on the web due
// to its ease of use
//
// Dedication:
// Thomas William Rhys Davids, Ven. Udagama Sumangala
// Rev. Fr. A. M. Gunasekara, Rev. Fr. Theodore G. Perera
// Ven. Mettavihari
//
// Maintainer:
// JC Ahangama - sing@ahangama.com
//
partial alphanumeric_keys modifier_keys
xkb_symbols "us" {
  name[Group1]= "Singhala (US, Modified for Singhala Hodiya)";
  include "us(basic)"
  include "level3(alt_switch)"
//
//                   UNSHIFTED,         SHIFT,           ALT
//                   --------------------------------------------
//
  key <AB01> { [             z,    VoidSymbol,    VoidSymbol ] };
  key <AB02> { [             x,    VoidSymbol,    VoidSymbol ] };
  key <AB03> { [             c,      ccedilla,    VoidSymbol ] };
  key <AB04> { [             v,    VoidSymbol,    VoidSymbol ] };
  key <AB05> { [             b,             B,    VoidSymbol ] };
  key <AB06> { [             n,             N,        ntilde ] };
  key <AB07> { [             m,    VoidSymbol,    VoidSymbol ] };
  key <AB08> { [         comma,          less,           UAB ] };
  key <AB09> { [        period,       greater,           UBB ] };
  key <AB10> { [         slash,      question,         U200C ] };

  key <AC01> { [             a,        aacute,    adiaeresis ] };
  key <AC02> { [             s,    VoidSymbol,    VoidSymbol ] };
  key <AC03> { [             d,             D,    VoidSymbol ] };
  key <AC04> { [         thorn,             f,    VoidSymbol ] };
  key <AC05> { [             g,             G,    VoidSymbol ] };
  key <AC06> { [             h,    VoidSymbol,    VoidSymbol ] };
  key <AC07> { [             j,      ccedilla,    VoidSymbol ] };
  key <AC08> { [             k,    VoidSymbol,    VoidSymbol ] };
  key <AC09> { [             l,             L,   ocircumflex ] };
  key <AC10> { [     semicolon,         colon,    VoidSymbol ] };
  key <AC11> { [    apostrophe,      quotedbl,    VoidSymbol ] };

  key <AD01> { [           eth,           ETH,             q ] };
  key <AD02> { [            ae,         acute,    VoidSymbol ] };
  key <AD03> { [             e,        eacute,    ediaeresis ] };
  key <AD04> { [             r,   ucircumflex,    VoidSymbol ] };
  key <AD05> { [             t,    VoidSymbol,    VoidSymbol ] };
  key <AD06> { [             y,    VoidSymbol,    VoidSymbol ] };
  key <AD07> { [             u,        uacute,    udiaeresis ] };
  key <AD08> { [             i,        iacute,    idiaeresis ] };
  key <AD09> { [             o,        oacute,    odiaeresis ] };
  key <AD10> { [             p,    VoidSymbol,    VoidSymbol ] };
  key <AD11> { [   bracketleft,     braceleft,    VoidSymbol ] };
  key <AD12> { [  bracketright,    braceright,    VoidSymbol ] };

  key <AE01> { [           one,        exclam,   dead_macron ] };
  key <AE02> { [           two,            at, dead_belowdot ] };
  key <AE03> { [         three,    numbersign, dead_abovedot ] };
  key <AE04> { [          four,        dollar,      currency ] };
  key <AE05> { [          five,       percent,           UB0 ] };
  key <AE06> { [           six,   asciicircum,    onequarter ] };
  key <AE07> { [         seven,     ampersand,       onehalf ] };
  key <AE08> { [         eight,      asterisk, threequarters ] };
  key <AE09> { [          nine,     parenleft,    VoidSymbol ] };
  key <AE10> { [          zero,    parenright,    VoidSymbol ] };
  key <AE11> { [         minus,    underscore,         U2014 ] };
  key <AE12> { [         equal,          plus,    VoidSymbol ] };

  key <BKSL> { [     backslash,           bar,    VoidSymbol ] };
  key <SPCE> { [         space,  nobreakspace,    VoidSymbol ] };
  key <TLDE> { [         grave,    asciitilde,    VoidSymbol ] };
};

=============END VARIANT PROGRAM TO ADD TO symbols/lk=============




2. PLEASE ADD TO base.xml AS THE LAST VARIANT UNDER lk

==========LAST VARIANT UNDER lk LAYOUT IN base.xml FILE===========

        <variant>
          <configItem>
            <name>us</name>
            
            <shortDescription>si-us</shortDescription>
            <description>Singhala (US, Modified for Singhala Hodiya)</description>
            <languageList>
              <iso639Id>sin</iso639Id>
            </languageList>
          </configItem>
        </variant>

================END TEXT LINES TO ADD TO base.xml=================





3. PLEASE ADD THIS LINE TO THE base.lst file AS FIRST VARIANT FOR lk

=======LINE TO ADD UNDER '!variant' SECTION OF base.lst file======

         us              lk: Singhala (US, Modified for Singhala Hodiya)

==============END LINE TO BE ADDED TO base.lst file===============